What causes knee pain when bending and straightening the leg?

When you bend or straighten your knee, many parts have to work together. Sometimes, the pain happens because the cartilage that cushions your joint is worn away, as seen in arthritis. This makes the surfaces of your knee rub together, causing pain. The tendons that connect your muscles to your knee, like the quadriceps or patellar tendon, can also become irritated or inflamed (a condition called tendonitis).

Another common cause is an issue with how the patella, or kneecap, moves within its track. If it doesn't move smoothly, it can rub against the bone and hurt. In some cases, there might be injury to the knee's soft tissues from overuse or a sudden twist, leading to strains or small tears in the ligaments or tendons.

If you're experiencing knee pain and want to better understand what might be causing it, try our free AI symptom checker to get personalized insights. Understanding the cause of the knee pain helps in guiding the best treatment and exercises for healing and strengthening the knee.